Hi all, It's been a while since I have posted anything, but today I have some good news! After fighting with bubbles in my fuel lines, on my Lazair, for a few years now(I run 210cc Solo engines) I have finally solved the problem. I wished I could have known this solution when I had the Rotax 185's on my plane, as it always had bubbles in the line as well. It was a combination of my problem and another pilot with an Ercoupe aircraft that had to set his plane down, because he used Premium car gas(vapor lock problem). Since he switched back to avgas, his plane is flying well again. I did some research on avgas and it is more resistant to vapor lock, among other good qualities. So I mixed up a tank of avgas 100LL at 33-1 mix and ran the engines, no bubbles at all, at any throttle setting! The engines run smoother. I let them run at idle for awhile, then gunned it to full throttle, perfect! No hesitation at all (with Premium car gas, it would always hesitate after long idles)! So I took a short flight after a few hops to make sure I wasn't dreaming. Wow! It's a completely different airplane. So this is my first and only flight so far, but it sure looks promising! I will post again when I get more and longer flights in. I had tried so many different set ups with the fuel lines, I even tried small "buffer" tanks near the engine to get rid of the bubbles before going into the engines. One thing that did work was an electric fuel pump pushing the gas up, but I don't have a strong enough power source to keep the battery charged for the electric pump, and I would have to have 2 pumps, one for each engine for reliability. Avgas is the answer for me and probably for anyone else that has bubbles in their fuel lines. FYI Daffy

Thanks for that info Daffy. I'm running Pioneers and at the time they (chainsaws) were in production they were designed for leaded low octane auto gas. Because of this I was concerned about the low lead high octane fuel such as 100LL I did an internet search (the only reason I know anything at all!) and I found this very interesting article that made me feel a little more comfortable; however, one sentence in the article does concern me and that is the higher potential for carbon build up and plug fouling but that's yet to be see if it will be an issue with my engines. Thanks again for the post.Russell

Hi Russel, !00ll stands for low lead, so I would think it would be ok to use in your pioneers. You could check the plugs at first, more often to be sure. Being higher octane (which means it's slower burning) you might lose a little power, but from what I read, the engines will run a tad cooler because of this. I will bet they will run better than ever, as I found this out with my engines. Daffy

I resolved ALL of my 185 fuel line bubble problems COMPLETELY and ABSOLUTELY by simply going with smaller fuel line than what I had been using (Common size Blue line). I'm using a similar set-up to the factory supplied-advised system (see Series III manual). The exception is that I'm using stainless-steel adapters-spilcers-reducers-increasers (Carb Inlet turrets and In-tank filter connections) rather than just simple and ineffective wired-on larger fuel line increaser sections. Absolutely no problems (or bubbles) after a good number of trouble-free flying hours.

Hi Shannon,That's interesting and a bit strange at the same time. The reason I say that is that back when the pump bulbs were used on the Pioneers they were plagued with bubble issues. Then Dale recommened removing the bulb and that eliminated the bubble problem. For the eight years after that I flew I never once had a problem. Hang on I'm going somewhere with this. When I recently refurbished my plane I downsized the fuel lines in order to reduce the required vaccum pressure on the carb diaphram. What resulted was bubbles in the lines.Of course you have the 185's and I the Pioneers so that could very well explain the difference in results and too like my granny used to say, "what's good for the goose is not always good for the gander"! (You have to remember I'm in deep south Georgia and we have some pretty strange sayings!)

I really can't speak on your system Russell. Something changed evidently.... lineID, filter construction, diaphragm, fuel...something ?? What I can tell you is that for me the 185 bubble problems increased through the years as larger and larger lines were put into service. The "Blue" line that I used for a good period did produce some small bubbles but they never seemed to affect the engines. Wanting to upgrade the quality of the fuel lines I tried the Tygon F4040A. It was a larger size than I'd ever used before and would easily slip over the carb and filter barb connections. I had nothing but a steady train of bubbles with that set-up. So in thinking about it I decided to go back to a more or less "original type" set-up and well what do you know.

Last edited by Shannon on Thu Sep 29, 2011 10:23 am, edited 1 time in total.

Nope, all things stayed the same except the line size. As you know this subject has been discussed many times and the bottom line it seems is that everyone's situation is unique. Once during a static test stand run I found that when a line touched the stand a steady stream of tiny bubbles was created at that point. Sounds like a it will take a physics major to explain this!

Russell like I said I can't really comment in any meaningful way on you or Daffy's bubble problems and solutions. What I can add to the fray is that going back to an "established" approach has apparently solved my 185 bubble problems and it had nothing to do with fuel.

Anyway what I'm doing has tested out 100% positive on two planes after a good number of hours. Another plane will be rigged up shortly. Looking at it objectively I just reverted back to a factory type set-up (with a minor revision i.e. adapters) so that explains why it is working properly. Another benefit is that the fuel pulls up the small line set-up faster than with the larger "Blue" or Tygon lines. One or two shots of prime and the fuel is coming up the lines fast like it should.